seen_recent: separate current vs pre-compaction seen sets

Present the two seen sets separately to the surface agent:
- Current: already in context, don't re-surface
- Pre-compaction: context was reset, re-surface if still relevant

This lets the agent re-inject important memories after compaction
instead of treating everything ever surfaced as "already shown."

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

poc-memory/src/agents/defs.rs

@@ -495,36 +495,61 @@ fn resolve_seen_recent() -> String {
     }
 
     let state_dir = std::path::PathBuf::from("/tmp/claude-memory-search");
-    let mut entries: Vec<(String, String)> = Vec::new();
 
-    for suffix in ["", "-prev"] {
+    let parse_seen = |suffix: &str| -> Vec<(String, String)> {
         let path = state_dir.join(format!("seen{}-{}", suffix, session_id));
-        if let Ok(content) = std::fs::read_to_string(&path) {
-            entries.extend(
+        std::fs::read_to_string(&path).ok()
+            .map(|content| {
                 content.lines()
                     .filter(|s| !s.is_empty())
                     .filter_map(|line| {
                         let (ts, key) = line.split_once('\t')?;
                         Some((ts.to_string(), key.to_string()))
                     })
-            );
-        }
-    }
+                    .collect()
+            })
+            .unwrap_or_default()
+    };
 
-    if entries.is_empty() {
+    let current = parse_seen("");
+    let prev = parse_seen("-prev");
+
+    if current.is_empty() && prev.is_empty() {
         return "(no memories surfaced yet this session)".to_string();
     }
 
-    // Sort newest first, dedup
-    entries.sort_by(|a, b| b.0.cmp(&a.0));
-    let mut seen = std::collections::HashSet::new();
-    let recent: Vec<String> = entries.into_iter()
-        .filter(|(_, key)| seen.insert(key.clone()))
-        .take(20)
-        .map(|(ts, key)| format!("- {} (surfaced {})", key, ts))
-        .collect();
+    let mut out = String::new();
 
-    recent.join("\n")
+    // Current: already in this context, don't re-surface
+    if !current.is_empty() {
+        out.push_str("Already surfaced this context (don't re-surface unless conversation shifted):\n");
+        let mut seen = std::collections::HashSet::new();
+        for (ts, key) in &current {
+            if seen.insert(key.clone()) {
+                out.push_str(&format!("- {} (surfaced {})\n", key, ts));
+            }
+        }
+    }
+
+    // Prev: surfaced before compaction, MAY need re-surfacing
+    if !prev.is_empty() {
+        let current_keys: std::collections::HashSet<_> = current.iter()
+            .map(|(_, k)| k.as_str()).collect();
+        let prev_only: Vec<_> = prev.iter()
+            .filter(|(_, k)| !current_keys.contains(k.as_str()))
+            .collect();
+        if !prev_only.is_empty() {
+            out.push_str("\nSurfaced before compaction (context was reset — re-surface if still relevant):\n");
+            let mut seen = std::collections::HashSet::new();
+            for (ts, key) in prev_only {
+                if seen.insert(key.clone()) {
+                    out.push_str(&format!("- {} (pre-compaction, {})\n", key, ts));
+                }
+            }
+        }
+    }
+
+    out.trim_end().to_string()
 }
 
 /// Resolve all {{placeholder}} patterns in a prompt template.